This invention relates in general to control mechanisms for hydraulic circuits and, in particular, to a valve system selectively actuable in response to movement of a control member.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a control system for controlling the flow of hydraulic fluid to hydraulic motors in response to movement of a control member which may be retained in predetermined positions to effect and maintain fluid communication of hydraulic circuits.
Hydraulic circuits are utilized in many applications to effect movement or operation of various hydraulically driven mechanical equipment. In certain of such applications, for example construction machinery or earthmoving equipment, hydraulic circuits are utilized to control and effect movement of such things as dozer blades, loading buckets and other various attachments or accessories. These hydraulic circuits are utilized to control various positions of the dozer blade such as pitch, tilt and doze to enable various functions to be performed with the machine.
During operation a machine operator controls such functions by actuation of control levers to effect fluid communication of various hydraulic circuits to actuate hydraulic motors effecting such blade movement. Since the machine operator is required to continuously use these control levers in order to actuate such machine accessories or auxiliary equipment, various attempts have been made to provide automatic actuation features whereby a single operation of a control lever will automatically effect a desired operation of the accessory equipment without having to continuously manually manipulate the levers. Such control systems greatly improve operator efficiency and safety by allowing the machine operator to effect a desired movement by placing the control lever into a fixed position thereby freeing the operator's hands from the controls for performing other operations. Examples of various hydraulic actuating mechanisms which are used to attain such dependent or interrelated movement are disclosed in H. E. Beck, U.S. Pat. No. 3,122,247 and J. S. Pilch, U.S. Pat. No. 3,155,253. Each of these patents discloses hydraulic circuits and mechanical linkage which permits the machine operator to effect semi-automatic operation of the accessory equipment through a single manipulation of a control lever.
While the systems described in these patents are designed to aid the machine operator, such systems are expensive and complex.
The present invention relates to a more simple and, therefore, reliable control system for maintaining fluid communication in a hydraulic circuit.